- Title
- Managing pond breeding frogs in the forests of Eastern NSW
- Creator
- Lemckert, Francis Laurence
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2010
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Environmental sustainability in managing forestry impacts on wildlife in New South Wales (NSW) is vital for Forests NSW, the agency overseeing timber harvesting in the state. Protecting native species populations to ensure their future survival is essential. Timber harvesting in NSW occurs primarily along the coast and adjacent ranges in central and northern areas. Selective logging is used (not clearfelling), with strategies like buffers around riparian zones, retaining hollow-bearing trees, downed woody debris, and undisturbed vegetation corridors to mitigate impacts on wildlife. This region, between Latitudes 30° and 34° South, is dominated by native temperate wet and dry sclerophyll forests, stretching from coastal lowlands to montane areas over 1,000 meters high. The region hosts two anuran families: Hylidae (approx. 25 species) and Myobatrachidae (approx. 20 species), which have evolved here for over 60 million years. Understanding frog habitat requirements is crucial for effective protective measures. Scientific data on frog responses to disturbances under these measures help assess their effectiveness. Studies on pond-breeding frogs were conducted to understand their habitat needs and guide protective measure placement. Tests were done to evaluate the relationship between forestry disturbances and frog pond usage, assessing the effectiveness of current protective measures. Monitoring data was also reviewed to enhance strategies for sustainable frog management in the future. Additionally, frog distribution records were analyzed to assess the value of the current protected area system in safeguarding frog species in the study region and across Australia. Research involved surveys of anurans at 93 semi-permanent and permanent ponds in the Watagan Mountains, Bulahdelah, Wauchope, and Dorrigo areas. Surveys, conducted multiple times between 2001 and 2008, included aural and visual nocturnal searches across different seasons to gather long-term data on species presence at these sites. Species presence and abundance at each pond were recorded, along with micrometeorological data. Daytime visits were made to gather data on the breeding pond and habitat variables within an 80-meter radius. A basic understanding of the habitats frogs use is essential for determining the management area needed for ongoing conservation. A review of published studies on frog movements provided data on their habitat requirements and usage patterns, emphasizing the need to manage both breeding ponds and surrounding habitats. Field guides often provide vague or variable calling seasons for anuran species in the study region. An objective assessment of calling seasons in eastern mesic NSW was developed to accurately identify each species' core calling period, the months during which they are most likely to call and be surveyed effectively. This assessment defined the core calling period for each species as the months covering over 90% of calling records. The analysis of 17,461 records covering 67 species established core calling periods for 46 species. Of these, 43 species had clear core calling seasons centered on spring-summer, two called year-round, and one had an uncertain season, likely calling year-round. Increased latitude usually resulted in a slight reduction in the core calling period. This information confirmed the appropriate timing of surveys in this study and will enhance future research, management, and conservation outcomes. Micrometeorological variables like temperature and rainfall significantly influence anuran calling activity, though this has been under-studied in Australia. Frog calling records from this study were compared with temperature, humidity, and rainfall data from the previous 24 and 72 hours to assess their impact on calling activity. Models for nine species found that calling activity related to at least two of these variables. Calling showed a positive relationship with 72-hour rainfall in eight species and no relationship in one. Six species showed a positive relationship with 24-hour rainfall, while two had a negative relationship and one showed no relationship. Temperature and humidity had mixed impacts, showing positive, negative, or no relationship with calling. Rainfall over the previous 72 hours appears to be the best predictor for planning surveys. Other factors, like social environment and circannual rhythms, may interact with micrometeorology, leading to complex results requiring further study. These results suggest the study's surveys were appropriately timed for good data collection. Identifying specific habitat features correlated with frog presence/absence is crucial for frog management. This information helps identify likely breeding sites, critical habitat elements for survival, and how human-induced modifications may impact local frog populations. Managing forest frogs requires consideration of multiple environmental scales and features—no single pond type suits all frogs. Conservation of rare and threatened species is a priority, relying on identifying their specific habitat needs or specializations. The heath frog, Litoria littlejohni, is a rarely observed threatened species limited to the Watagan Mountains. It is protected by broad buffer zones around breeding sites, though its protection efficacy is uncertain. The species' persistence at sites logged and burnt multiple times suggests it can cope with some disturbance. Effective monitoring of anuran populations to detect early changes is vital for ongoing management. Regular data assessment is crucial to ensure monitoring programs have the statistical power to detect significant population changes. The power of the current monitoring program for the threatened northern corroboree frog (Pseudophryne pengilleyi) was evaluated for its sensitivity to detect increases and declines in the number of calling males at 14 sites. Despite the frog's consistent and easily monitored calling behavior, detecting changes is challenging due to inter-year variance in counts. Developing effective monitoring programs for species with inconsistent calling spread over long seasons is difficult and resource-intensive. Wildlife management practices in production forests should be complemented by ensuring species are adequately represented in protected areas (PAs). PAs can support populations that migrate into production forests, maintaining metapopulations and genetic flows. The relative reservation status of anuran species in Australia was determined using the Australian Natural Heritage Tool Database (ANHAT), a large database with multiple sources of anuran site records. The number of records for each species inside and outside protected areas was noted, along with the number of reserves where each species was recorded. Poorly "reserved" species were found in northern Australia or poorly protected agricultural belts in eastern and western Australia. In contrast, forest-dwelling species from eastern NSW are relatively well recorded in PAs. Species dependent on native vegetation in agricultural areas face the most pressing conservation challenges. Forestry management practices include controlled burns to reduce the risk of high-intensity, uncontrolled wildfires that threaten forest assets. The impact of controlled burns on wildlife, particularly anurans, is widely debated. A study in the Dorrigo area compared trends in anuran counts at four burnt "experimental" ponds with those at four unburnt "control" ponds. The analysis found no significant difference in trends between burnt and unburnt ponds. The region's fauna and flora have evolved under regular fire exposure, and local anurans may have developed strategies to cope with low-intensity fires. Current protection of anurans in NSW forests focuses on retaining undisturbed habitat areas, especially protecting ponds and the adjacent 20-30 meter vegetation bands. Linkage corridors of undisturbed vegetation are also necessary for migration. For threatened species, larger protection zones are often established, with fire exclusion being a key conservation element. Hydrology research suggests that 20-30 meter buffer zones around breeding sites protect water quality and reproductive activities. However, this buffer may not significantly protect the surrounding forest used as non-breeding habitat. Where forestry activities pose a genuine threat to a species, the buffer should be expanded to at least 300 meters. Studies on habitat relationships indicate that anurans in the region do not have specialized habitat requirements that become unusable through disturbance. No clear negative relationships were found between logging, fire, or grazing and the presence/absence or abundance of anurans. Generally, anurans appear robust to the types of forest habitat modifications resulting from selective logging, and buffer zones greater than 20 meters are unlikely needed to maintain populations in such environments. Species with narrow habitat requirements, like rainforest/wet forest specialists, may require special consideration in management plans.
- Subject
- anurans; conservation; habitat requirements; forestry impacts; monitoring
- Identifier
- http://hdl.handle.net/1959.13/44573
- Identifier
- uon:5831
- Rights
- Copyright 2010 Francis Laurence Lemckert
- Language
- eng
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